On the anniversary of John Kennedy’s death, Americans should feel grateful that it’s been fifty years since any president has died in office. By contrast, in the 120 years before Kennedy, our sitting chief executives perished far more regularly—dying in office with stunning regularity at a rate of once every 15 years.

The improved survival rate reflects vastly better health care—in fact, four of our six longest-lived presidents served their terms after JFK. Even in the case of assassinations, this connects to medical advances: McKinley and certainly Garfield could have survived their shootings with modern medicine and Reagan, shot in the chest in 1981, would likely have died in previous centuries. Reagan like all five presidents from Nixon through the first Bush, lived more than 80 years, and the three latest incumbents stand good chances for similar longevity.